The present invention relates to pulse engineering, and more particularly to methods of producing start pulses in a periodic motion process and to devices for effecting same.
The invention can most advantageously be used in internal combustion engines for producing sparking or fuel injection start pulses.
At present, the growth of the automotive industry is tremendous. In this connection, more stringent requirements are imposed on the performance of internal combustion engines and on the toxicity of the exhaust gases, both characteristics being to a great extent determined by the optimality of operation of the ignition or fuel injection system.
Besides, the existing methods of producing start pulses in a periodic motion process and devices for effecting same are not accurate and flexible enough in initiating sparking or fuel injection.
Known in the art is a method of producing start pulses in the process of a periodic motion (cf. FRG Pat. No. 2,010,999; Cl. G02, p 5/08, July 4, 1974), comprising generation, at the moment a given periodic motion phase is reached, of a basic train of periodic motion phase pulses with simultaneous generation of a main time interval and storage, during the main time interval, of an initial train of periodic motion phase pulses forming part of the basic train, and generation, at the moment the next periodic motion phase is reached, of a start train of periodic motion phase pulses with simultaneous addition of the periodic motion phase pulses in the start and initial trains, with a start pulse being produced as soon as the result of the addition of the periodic motion phase pulses in the start and initial trains becomes equal to a preset value.
This prior art method, however, does not permit the duration of the main time interval to be varied with due account for the periodic motion speed variation pattern.
In addition, in the prior art method, the periodic motion speed is measured well before a start pulse is produced, whereby the dynamic error is increased.
At the moment start pulses are produced by the prior art method, there is no consideration or account taken of the parameters of physical factors (load, temperature, humidity, etc.) influencing the periodic motion.
Another disadvantage of the known method is due to the fact that because of the non-multiplicity of the periodic motion phase pulses within the duration of the main time interval, the periodic motion phase pulses in the initial train, the number of which is proportional to the average periodic motion speed, are determined with an error lying within the limits of a periodic motion phase. This, in turn, make it impossible to produce a start pulse with an accuracy better than such limits. Therefore, the error in producing start pulses in the low rpm range, when the main time interval includes a small number of periodic motion phase pulses, is substantial.
Further, when the prior art method is used for objects with a small number of specific or distinct periodic motion phases, the magnitude of the error in producing start pulses limits their use without additional improvements.
A device for producing start pulses in a periodic motion process by the prior art method is known. The device comprises a sensor of a given periodic motion phase, connected to a main time interval generator, to a counter and to a control unit, and a sensor of periodic motion phase pulses, connected to the control unit.
The prior art device does not consider or take into account those periods of the periodic motion phase pulses which are included in the main time interval. As a result, the accuracy of producing start pulses is determined by the limits of a periodic motion phase and, just as in any digital system, it cannot be better than +1 pulse, that is, +1 specific periodic motion phase. For example, if the control member is a vehicular engine flywheel having about 130 teeth, the accuracy of producing start pulses at low rpm cannot be better than 360.degree./130.degree..apprxeq.2.8.degree., although the ignition advance angle varies within 5.degree. to 35.degree.. Thus, in the low rpm range, the error in producing start pulses may be 50% and higher.
In addition, in the known device, the periodic motion speed, which is the number of pulses in the initial train, is determined well before the start train of periodic motion pulses which results in a substantial dynamic error, particularly under such transient conditions as rundowns or runups. In this case, in the low rpm range, for example, in vehicular engines, the rotational speed varies up to 30% and above per crankshaft revolution.
In order to attain high accuracy in producing start pulses by the prior art device, the control member has to be improved. Therewith, an additional mask with a greater number of specific periodic motion phases must be placed on the control member or the control member itself must be improved. This leads to additional expenses and low efficiency of the device.